feat(opencode): wire 29-point CLI lifecycle scripts, drift-C reconciler, and skill docs

.agents/skills/multi-agent-mux-create/SKILL.md

@@ -129,7 +129,7 @@ herdr_sessions:
 
 ```bash
 WORKSPACE=/path/to/project
-AGENT=claude  # claude | agy | hermes | grok — always pass it explicitly
+AGENT=claude  # claude | agy | hermes | grok | opencode — always pass it explicitly
 source .agents/skills/lib.sh
 SESSION_NAME="$(derive_session_name "$WORKSPACE" "$AGENT")"
 
@@ -160,7 +160,10 @@ case "$AGENT" in
   grok)
     herdr new-session -d -s "$SESSION_NAME" -x 140 -y 40 -c "$WORKSPACE" "grok --permission-mode bypassPermissions"
     ;;
-  *) echo "ERROR: --agent must be claude, agy, hermes, or grok, got: $AGENT"; exit 2 ;;
+  opencode)
+    herdr new-session -d -s "$SESSION_NAME" -x 140 -y 40 -c "$WORKSPACE" "opencode --auto --agent build"
+    ;;
+  *) echo "ERROR: --agent must be claude, agy, hermes, grok, or opencode, got: $AGENT"; exit 2 ;;
 esac
 
 # 3. Wait for agent TUI to be ready (varies: claude ~5s, agy ~3s)